The structure and composition of nucleic acid material, including genetic material, especially gene sequencing and the identification of genetic markers associated with specific disease, is becoming more important. Within biomedical and pharmaceutical industries and associated research, more emphasis is being placed on accurate and speedy gathering of information. In particular the genetic patterns connected with disease or reactions to medications should be accessed quickly with an aim to provide genetic information for point-of-care applications. Methods and devices are being developed to facilitate this.
It has been discovered that biosensor elements can be capable of identifying individual DNA strands with single base resolution, a base being one of four possible types of molecules (A, C, G or T) used to encode information in the DNA. In particular, so-called nanopores are utilized. These are apertures in a thin layer, typically 100 nm or smaller, formed in many possible geometrical shapes. Segments of the genetic material to be sequenced are passed through or forced through the aperture. The shape of the samples or the temporary binding of the molecules of the samples with the molecules of the nanopore cause registration in the detection device characteristic of the various bases, thereby facilitating sequencing. A nanopore may be biological or synthetic in origin. Each nanopore is specific for a desired detection and can therefore be made into a detector for a specific gene sequence, such as that associated with a particular cancer mutation, or for an SNP (single nucleotide polymorphism), for example associated with a drug response in anaesthesia or chemotherapy. The use of nanopores allows rapid detection compared with current sequencing devices.
US patent application 2007/0054276 discusses polynucleotide analysis systems and methods of nanopore analysis, and how to rapidly determine the sequence of a nucleic acid molecule for identifying genetic mutations and polymorphisms. It discloses the concept of nanopore sequencing as based in the property of physically sensing the individual nucleotides or physical changes in the environment of the nucleotides (e.g. electric current) within an individual polynucleotide as it traverses through a nanopore aperture. The SNP can be identified using the nanopore analysis system to measure an electronic signature (e.g. ion current or tunneling current) of the modified target polynucleotides, the electronic signatures of modified and non-modified molecules being distinguishable. The nanopore detection system used comprises electronic equipment capable of measuring the electronic characteristics of the interaction between nanopore aperture in a structure of the nanopore detection system and the polynucleotide. A computer system controls the electronic measurement and handles the data produced. Volume, shape or charges on each monomer can affect conductance in a characteristic way. A voltage gradient is applied to the nanopore device to draw the target polynucleotide from one side of the aperture to the other.
US patent application 2007/0048745, from the same applicant, further discloses devices, systems and methods for nanopore analysis of polymers.
Papers in J. Amer. Chem. Soc. 128 (2006) 1705 and Nature Biotech 19 (2001) 636, disclose the use of biological nanopores for sequence specific detection of individual DNA strands using engineered nanopores. Binding of the DNA strand molecules to molecules in the nanopore causes changes in an ionic current flowing through the nanopore.
Present work focuses on a nanopore detection and readout for a specific gene sequence. The devices make only one specific measurement on a sample.
A problem with these current devices and methods is that acquiring information for more than one target sequence is slow, requiring repetitive measurements.
It is thus an object of the invention to provide an improved device which can provide more sequencing information, faster.